Basic Science Orthobullets/Millers Book Flashcards

Question

What are measures of shock recovery?

Answer 1

Lactate—indirect marker of tissue hypoperfusion • **Best measures of adequate resuscitation:** _Clinical measure_ of organ function: urine output more than 30 mL/h _Laboratory measure:_ serum lactate less than 2.5 mg/dL

Answer 2

**Neurogenic shock** High spinal cord injury (also anesthetic accidents) Loss of sympathetic tone and of vasomotor tone of peripheral arterial bed Bradycardia, hypotension, warm extremities **Treatment: vasoconstrictors and volume** • **Septic shock (vasogenic)** Number one cause of ICU death Mortality 50% Bacterial toxins stimulate cytokine storm. Examples: gram-negative lipopolysaccharides, toxic shock superantigen Inflammatory mediators cause endothelial dysfunction and peripheral vasodilation • Treatment: **Identification and treatment of infections** **Prompt resection of dead tissue** **Appropriate antibiotics** **Cardiogenic shock** _Bad pump:_ Extensive MI, arrhythmias _Blocked pump (obstructive shock)_ Massive “saddle” pulmonary embolism Tension pneumothorax Cardiac tamponade Beck triad: hypotension, muffled heart sounds, neck vein distension Pulsus paradoxus Decreased systolic BP with inspiration Treatment: pericardiocentesis **Hypovolemic shock:** Most common shock of trauma Volume loss from bleeds or burns “Third spacing” also a cause Neuroendocrine response: save heart and brain Peripheral vasoconstriction BP may be normal Pale, cold, clammy extremities **Percentage of blood loss key to symptoms/signs:** Class I: up to 15% blood volume loss Vital signs can be maintained. Pulse below 100 beats/min Class II: 15%–30% blood volume loss Tachycardia (\>100 beats/min), orthostatic, Anxious Increased diastolic BP Class III: 30%–40% blood volume loss Decreased systolic BP Oliguria Confusion, mental status changes Class IV: more than 40% blood volume loss Life threatening; patient is obtunded Narrowed pulse pressure IImmeasurable diastolic BP Treatment **First, ABCs of resuscitation: then, bleeding must be stopped.** **Blood products make better resuscitation fluids than saline.**

Answer 3

Higher in cases that involve thorax such as scoliosis Highest in patients with prior disease Spinal/epidural anesthesia favored over general Medical treatment should be maximized around surgery. Symptomatic COPD: **anticholinergic inhalers (ipratropium;** May require corticosteroids Asthma **Presence of wheezes or shortness of breath: β-agonist inhalers (albuterol)** Perioperative oral steroids safe Systemic glucocorticoid should be considered if forced expiratory volume in 1 minute (FEV1) or peak expiratory flow rate (PEFR) is below 80% predicted values/personal best. Postoperative atelectasis Like the associated cough, the workup is usually nonproductive. Deep breathing/incentive spirometry—equally effective Postoperative pneumonia takes up to 5 days to manifest. Productive cough, fever/chills, increased WBC count Radiograph: pulmonary infiltrates _Smoking cessation improves outcomes_ **Patients should stop 6–8 weeks preoperatively.** **Nicotine supplements do no harm to wound.** Fewer pulmonary complications • Smokers have six times more pulmonary complications. Fewer wound healing issues and wound infections • Lower nonunion rate • Shoulder, neck, and thoracic pain in smokers Prompts careful evaluation of lung fields Superior sulcus tumor (Pancoast tumor) Intrinsic atrophy of hand—C8–T1

Answer 4

Pulmonary failure due to edema (see Fig. 1.56A) Pathophysiology Complement pathway activated Increased pulmonary capillary permeability Intravascular fluid floods alveoli Results **Hypoxia, pulmonary HTN** **Right heart failure** 50% mortality Etiology Blunt chest trauma, aspiration, pneumonia, sepsis Shock, burns, smoke inhalation, near drowning Orthopaedic: Long-bone trauma Clinical symptoms Tachypnea, dyspnea, hypoxia, decreased lung compliance Pao2/fio2 ratio below 200 Imaging: Radiographs: diffuse bilateral infiltrates, “snowstorm” CT: ground glass appearance Treatment: Aggressive supportive care Prompt diagnosis and treatment of musculoskeletal infections:Prompt treatment of long-bone fractures Ventilation with positive end-expiratory pressure (PEEP) 100% O2

Answer 5

Petechial rash: fat to skin Neurologic symptoms: fat to brain Mental status changes: confusion, stupor Rigidity, convulsions, coma Pulmonary collapse: fat showers lung ARDS: hypoxia, tachypnea, dyspnea Associated with long-bone fractures

Answer 6

Common inherited bleeding disorders: Vonwillebrands disease AD (Vonwillebrands factor) Hemophilia Ax-linked recessive Hemophilia B. Christmas Von Willebrand disease: **autosomal dominant** Most common genetic coagulation disorder **Von Willebrand factor dysfunction** Binds platelets to endothelium Carrier for factor VIII Treatment: desmopressin Hemophilia A (VIII): X-linked recessive Hemophilia B (IX) Christmas disease: X-linked recessive

Answer 7

Platelet-inhibitor drugs (aspirin, clopidogrel, prasugrel, NSAIDs) Drugs that cause thrombocytopenia Penicillin, quinine, heparin, LMWH Anticoagulants (see earlier discussion on DVT) Supplements Fish oil, omega-3 fatty acids, vitamin E Garlic, ginger, Ginkgo biloba

Answer 8

Tourniquets: tissue effect relates to time and pressure Used no longer than 2 hours Time to restoration of equilibrium 5 minutes after 90 minutes of use 15 minutes after 3 hours Prolonged use can cause tissue damage. Nerve damage compressive (not ischemic) Electromyography: subclinical abnormalities in 70% with routine use Slight increase in pain Wider tourniquets distribute forces Pad underneath prevents skin blisters in TKA • Lowest pressure needed for effect should be used 100–150 mm Hg above systolic BP 200 mm Hg upper extremity 250 mm Hg lower extremity

Answer 9

**Tranexamic acid** Synthetic lysine analogue; acts on fibrinolytic system Competitive inhibitor of plasminogen activation Reduces blood loss with no increase in DVT. **Temperature** Mild hypothermia increases bleeding time and blood loss. • Intraoperative “cell saver” may be cost-effective if: About 1000 mL of blood loss is expected Recovery of 1 or more unit of blood is anticipated. Techniques not yet found to be effective or cost-effective Bipolar sealant, topical sealants, autologous donation Reinfusion systems, routine transfusions over 8 g/dL Hb **Preoperative techniques to address anemia** Oral iron 30–45 days preoperatively Vitamin C increases iron absorbtion Folate and vitamin B12 deficiency also a source of anemia Erythropoietin if preoperative Hb below 13

Answer 10

Transfusions • Ratio of 1:1:1 blood product resuscitation is superior to saline fluid • Preoperative Hb most significant predictor of need • Various guidelines for when to transfuse • Hb less than 6 g/dL: transfusion • Hb 7–8 g/dL: transfusion of postoperative patients • Hb 8–10 g/dL: transfusion of symptomatic patients • Restrictive transfusion strategies • Lower 30-day mortality trend • Lower infection risk trend • Greatest benefits to orthopaedic patients • No difference in functional recovery □ Transfusions risks • Leading risk: transfusion of wrong blood to patient • Occurs in 1 in 10,000 to 1 in 20,000 RBC units transfused • Transfusion reactions **Febrile nonhemolytic transfusion reaction** Most common 1–6 hours post-transfusion From leukocyte cytokines released from stored cells Leukoreduction decreases incidence **Acute hemolytic transfusion reaction** Medical emergency ABO incompatibility IgM anti-A and anti-B, which fix complement Rapid intravascular hemolysis Classic triad: fever, flank pain, red/brown urine (rare) Can cause disseminated intravascular coagulation (DIC), shock, and acute renal failure (ARF) due to acute tubular necrosis (ATN) Positive direct antiglobulin (Coombs) test result **Delayed hemolytic transfusion reactions** Reexposure to previous antigen (i.e., Rh or Kidd) History of pregnancy, prior transfusion, transplantation 3–30 days post-transfusion Anemia, mild elevation of unconjugated bilirubin, spherocytosis Anaphylactic reactions: about 1 in 20,000 Rapid hypotension, angioedema Shock, respiratory distress Frequently involve anti-IgA and IgE antibodies Treatment: cessation of transfusions, ABCs of resuscitation, epinephrine Urticarial reactions: about 1%–3% Mast cell/basophils release of histamine—hives Infectious risks Bacterial: 0.2 per million packed red blood cell (PRBC) units transfused Gram-positive organisms Cryophilic organisms: Yersinia, Pseudomonas HTLV—approximately 1 in 2 million HIV—approximately 1 in 2 million Hepatitis C—approximately 1 in 2 million Hepatitis B—approximately 1 in 250,000

Answer 11

Liver failure: critical for producing proteins and metabolizing toxins • Laboratory findings • Increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin • INR above 1.5, low platelets (\<150,000 cells/μL) • Acute—most commonly viral and drug induced • Acetaminophen—number one cause in United States • Other toxins: alcohol, occupational, mushrooms • Viral hepatitis • Chronic—cirrhosis is end-stage fibrosis of liver • Common: hepatitis (B, C), alcoholism, hemochromatosis • Classifications can be helpful to estimate risks • Child classification—most widely used • Based on laboratory results and physical examination • Model for End-Stage Liver Disease (MELD) score (http://www.mayoclinic.org/medical-professionals/model-end-stage-liver-disease/meld-model) • Formula based on bilirubin, INR, creatinine • Studies highlight mortality at 90 days relative to MELD score • \<9: about 2% mortality • 10–19: about 6% mortality • 20–29: about 20% mortality • 30–39: about 53% mortality • \>40: about 71% mortality • Complication rates from surgery are extremely high. • In patients undergoing arthroplasty, MELD score above 10 predicted • Three times the complication rate • Four times the rate death

Answer 12

Large bowel dilation • Abdominal distension the prominent symptom • Colonic perforation should be avoided. • Risk factors • Elderly or male patient • Previous bowel surgery • Diabetes, hypothyroidism • Electrolyte disorders Radiographic findings Distended transverse and descending colon and cecum (see Fig. 1.58C) Colonic diameter more than 10 cm risks perforation. Treatment Nothing by mouth status Neostigmine Colonic decompression

Answer 13

Most common antibiotic-associated colitis Change in colon flora favors Clostridium difficile Makes enterotoxin-A and cytotoxin-B Many antibiotics Clindamycin, fluoroquinolones Penicillins and cephalosporins Can become severe fulminant colitis Toxic megacolon and perforations • Risk factors Elderly hospitalized patient Severe illness Antibiotic use Proton pump inhibitor use • Diagnosis Watery diarrhea with fever Leukocytosis, lower abdominal pain Laboratory findings WBC count more than 15,000 cells/μL Stool specimen should be tested for C. difficile toxin PCR or ELISA KUB (kidney, ureter, bladder) (plain abdominal) radiograph Toxic megacolon: greater than 7 cm Thumbprinting (see Fig. 1.58D) • Treatment Oral metronidazole Oral vancomycin (IV will not work) Fidaxomicin Colectomy if unresponsive and severe Megacolon, WBC count more than 20,000 cells/μL

Answer 14

Intermittent hypercapnia and hypoxia Decreased CO2-induced respiratory drive Extreme sensitivity to opioids Leads to • Pulmonary HTN Cardiac arrhythmias GERD (reflux) directly related to BMI Delayed gastric emptying Increased risks for aspiration/intubation Higher risk for complications (2–4 times greater) Respiratory failure, ICU transfers, increased length of stay Increased postoperative O2 desaturation Increased intubation, aspiration pneumonia, ARDS Increased MI, arrhythmias (atrial fibrillation) Screening tools: STOP-BANG (Fig. 1.59) - Snoring, tired, observed apnea, pressure (HTN) - BMI over 35, age older than 50 years, neck circumference larger than 40 cm, gender male Five or more factors present—high risk of severe OSA Best practices Initiation or continuation of CPAP use More than 2 weeks of preoperative CPAP improved HTN, O2 saturation, apneic events Pulmonary HTN: in 20%–40% of patients with OSA Preoperative serum bicarbonate predicts hypoxia in OSA Chronic respiratory acidosis Site of service (American Society of Anesthesiology consensus statement) Ambulatory surgery under local/regional—lower risk Avoid procedures requiring opioids—greater risk Comorbid conditions must be optimized for outpatient surgery. HTN, arrhythmias, CHF, cardiovascular disease, and metabolic syndrome. Metabolic syndrome = obesity, hypertension, hypercholesterolemia, dyslipidemia, and insulin resistance Avoidance of flat supine position; sitting position opens airway.

Answer 15

Autosomal dominant genetic defect of T-tubule of sarcoplasmic reticulum Ryanodine receptor defect (RYR1) Dihydropyridine receptors (DHP) Triggered by volatile anesthetics and succinylcholine Creates an uncontrolled release of Ca2+ Sustained muscular contraction (masseter rigidity) Increased end-tidal CO2 Earliest and most sensitive sign Mixed respiratory and metabolic alkalosis Hyperthermia is classic but occurs later. • Muscle damage Myoglobin from rhabdomyolysis can cause ARF. Elevated creatine kinase Hyperkalemia can lead to ventricular arrhythmias. **Treatment with dantrolene** Decreases intracellular Ca2+ Stabilizes sarcoplasmic reticulum Treatment of high serum potassium Hydration Cooling

Answer 16

Should be considered for every fluoroscopic case Increased radiation exposure associated with --Imaging of larger body parts --Positioning the extremity closer to the x-source --Use of large C-arm rather than mini C-arm Factors to decrease the amount of radiation exposure --Minimizing exposure time --Using collimation to manipulate the x-ray beam --Use of protective shielding --Maximizing the distance between the surgeon and the radiation beam --Utilizing mini C-arm whenever feasible (associated with minimal radiation exposure) --Surgeon control of the C-arm

Answer 17

Contraindications Pacemakers Cerebral aneurysm clips Shrapnel or hardware, in certain locations

Answer 18

Evaluation of peripheral nerves Nerve impulses stimulated and recorded by surface electrodes Allows calculation of conduction velocity Measures latency (time from stimulus onset to response) and response amplitude Late responses (F wave, H reflex) allow evaluation of proximal lesions. Impulse travels to the spinal cord and returns